Case of the Oil Fire Damper

On the east edge of Mishawaka, Ind., there is a large electrical substation that remains where the Twin Branch coal-fired generating plant once stood. The plant was built in the 1920s next to the St. Joseph River hydroelectric plant. The power from the hydro plant could be used to bring the coal-fired plant online after a cold shutdown. The river also furnished water for the steam condensers. The environmentalists convinced the power company to switch from coal to oil. When the oil embargo hit, they were told to switch back to coal. Lacking a sense of humor, the owners had the plant dismantled in the late 1970s.

A few years ago, there was an explosion and fire in a transformer. It was one of those fires that they just let burn until all the oil used to cool the transformer had been consumed. Not every firefighter wants to rush into an area where 138,000V is the norm and start spraying water from a fire hose. Oil and water are not a good combination, even without the high voltage. I don't remember if they tried foam. If they did, it didn't work.

After watching the fire for a while, I wondered if removing the oil from the transformer would help. You need fuel, heat, and air to keep a fire going. I'm wondering if it would be feasible to have an underground tank connected to a drain on the transformer. Something as simple as a ball valve could be connected to a long linkage. This would allow the valve to be opened from a safe distance. It could also be motorized. Gravity would allow the oil to flow into the underground tank. The tank might need to be kept purged with an inert gas just to be safe.

I've heard about aircraft in trouble dumping their excess fuel before landing. You have to wonder where that fuel goes after being jettisoned. Jet fuel does not evaporate like gasoline. My hunch is that the fuel is jettisoned to aid firefighters in the event of a fire. If it works for aircraft, it might work for transformers. If the oil could be contained in the underground tank, that might aid in the cleanup. The less oil there is leaking out on to the ground, the better. Murphy says that if you are ready for the fire, it won't happen.

I don't know if this system has ever been put into service, but it was apparently not at the Twin Branch fire.

This entry was submitted by Pete Ostapchuk and edited by Rob Spiegel.

Pete Ostapchuk was a radar operator on a Nike Hercules site in the Army, where he studied electronics through correspondence courses. He ended up in the electronics engineering department at CTS for eight years, where he worked on industrial automation projects. He also worked at Bayer for eight years in medical diagnostics R&D.

Tell us your experience in solving a knotty engineering problem. Send stories to Rob Spiegel for Sherlock Ohms.

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